1. Field
The present disclosure generally relates to digital audio devices, and more particularly, to techniques for suppressing transient audio artifacts and reducing power consumption in audio devices.
2. Background
Digital audio devices are electronic devices that produce sound from digital information. They include, but are not limited to, radio receivers, stereo systems, computers, audio playback devices, such as MPEG-1 Audio Layer 3 (MP3) players; landline telephones, cellular phones, personal digital assistants (PDAs), satellite radio receivers, audio visual systems, such as video players, and the like.
Two performance considerations in digital audio devices are the presence of audible artifacts and power consumption.
An audible artifact is a perceivable noise introduced into the sound output from the audio device, frequently caused by operation of the audio device itself. Audible artifacts are usually undesirable and represent a deviation from the fidelity of the audio input to the device.
Click-and-pop is a specific type of audible artifact. Click-and-pop is an unpleasant audible artifact produced by a speaker, which is often heard when an audio device powers up or powers down. Click-and-pop is generally caused by an abrupt transient voltage, e.g., a direct current (DC) offset across a speaker that may occur when an audio power amplifier transitions between operational modes, such as a power-off mode and power-on mode. Other operational modes may include a shutdown mode, where power is still applied to the audio power amplifier, but the audio signal itself is discontinued within the device. Click-and-pop can sometimes be heard when the audio signal is discontinued or resumed, i.e., transitioning to or from the shutdown mode, respectively.
Click-and-pop can be especially annoying when using headsets with audio devices. It has become quite common for consumers to use telephones, including cellular and convention landline telephones, through headsets or headphones (“headsets” collectively). Similarly, headsets are usually used with audio playback devices, such as MP3 players. Headsets may be wired or wireless, for example, Bluetooth™-enabled headsets. Due to a headset's close proximity to a user's ears during use, headset click-and-pop can be greatly annoying or even harmful to hearing. Therefore, there is a need in the art to reduce or eliminate click-and-pop in digital audio devices.
Another criterion affecting the design of digital audio devices, particularly portable communication and entertainment devices, is power consumption. For example, expected battery life of a portable device is inversely related to the power consumed by the device. Therefore, there is also a need in the art to reduce the power consumption in voice communication and audio reproducing/playing devices.